Rocket Warrior– cannot be destroyed by battle, but only on the player’s battle phase.

Blazing Mirror Force (Trap)- destroys all of the opponent’s monsters and deals half of their combined ATK as damage to each player. If the player damage can be negated, this card would dramatically lower the Deskbot player’s LP.

Barrel Behind the Door– if an effect would deal damage to the player, the damage is done to the opponent instead. Combining this card with Blazing Mirror Force could create an OTK if it succeeds.

Wall of Disruption– the opponent’s monsters lose 800 ATK per monster they control. As Deskbot’s usually run a full field of 5 monsters very quickly, this card would potentially keep Deskbot 009’s ATK at manageable levels.

Honest– when the player’s monster battles an opponent’s monster (in either player’s turn), the player can send Honest to the graveyard from their hand in order to increase the ATK of their monster by the ATK of the opponent’s monster. However, this only works if the player is battling with a Light-attribute monster.

Based on the cards so far, a good deck to use against Deskbots appears to need:

A strong Light attacker (to use Honest with).

Dragon-type monsters (who can be protected by spell cards and by Lord of D)

Fusion monsters equipped with either Battle Fusion or Time Magic Hammer.

Monsters:
3x Blue-Eyes White Dragon
1x Honest– Only one is allowed, so one it is.
2x Rocket Warrior– In theory, it can take off 500 ATK from a Deskbot, and then be fused into Rocket Hermos Cannon later to avoid taking damage.
2x Baby Dragon
2x Alligator’s Sword (these two are needed for Alligator’s Sword Dragon)
2x Lord of D– protects dragon-type monsters from being targeted, and can be used to make Time Magic Hammer.
3x The Dark Hex-Sealed Fusion– acts as a substitute to make Fusions easier. It also allows for summoning fusion monsters by tributing, so reduces the reliance on Polymerisations.
1x Kaiser Sea Horse– it only needs to stay alive for one turn, then can later be used to get Blue-Eyes more easily.
1x Blizzard Dragon
1x Black Dragon Collapserpent
1x White Dragon Wyverburster (the level 4 dragons are to make Dark Rebellion XYZ Dragon).

Extra Deck:
2x Rocket Hermos Cannon– attaches to a monster and allows that monster to make 2 attacks per battle phase and do piercing damage to defence position monsters.
3x Time Magic Hammer -for immortality.2x Alligator’s Sword Dragon– for direct attacks.
2x Doom Virus Dragon– destroys all monsters in the opponent’s field and hand with less than 1500 ATK.
3x Dark Rebellion XYZ Dragon– detaches two XYZ material to reduce the opposing monster’s ATK by half, then gives that attack to itself.
Two cards which would have been effective, Blue-Eyes Twin Burst Dragon and Starving Venom Fusion Dragon, are not yet in the game so unfortunately can’t be included. However, I’m still reasonably happy with this deck idea, now I just need to test it out.